On 08/05/2018 01:18, Jim Brain wrote: > > I'd recommend using 4kB pages, using one $d50x register to hold the > "task" number, and using 16 of the free registers to hold 16 "page" > registers, 1 for each 4kB page At 8bits, that'd be able to manage > 1MB, while extending the MMU regs to 13 bits would allow 32MB of > mapping. With a task register, you could have 256 mappings. The > additional 3 bits could be used for "IRQ on write, mark RAM as > read-only, and reserved. > The C128 was designed so you can configure all your banks and then switch between them with $ff0x accesses, without having to page the $d50x registers back in. Therefore I think you should consider adding a task register into the $ff0x range. I believe ram/rom shows through in $ff0x except where the existing registers are defined, so to remain backward compatible you'll need to enable it with a magic sequence in the $d50x range first.Received on 2018-05-08 11:00:02
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